1. Field of the Invention
This invention relates generally to wireless communication networks and methods, and more particularly to a method of maximizing the utilization of channel element resources in a base transceiver station by reserving a percentage of next-generation channel elements for certain types of calls that cannot be performed by previous generation channel elements. The benefit of the invention is more efficient utilization of resources. It also enables the delay of purchase of next generation channel elements, and thereby allows substantial capital expenditures to be deferred.
2. Description of Related Art
In a typical cellular wireless communication system (wireless telecommunications network), an area is divided geographically into a number of cell sites, each defined by a radio frequency (RF) radiation pattern from a respective base station. The base stations of the cells are then coupled to a switching system that provides connectivity to a transport network and/or to a signaling network. When a wireless client station, such as a cellular telephone, personal digital assistant, pager, or appropriately equipped portable computer, for instance, is positioned in a cell, the client station may then communicate via an RF air interface with the base station of the cell. Consequently, a communication path can be established between the client station and the network, via the air interface, the base station and the switching system.
As a general matter, each base station (or, more generally, cell site) in the system will include a number of channel element cards that pass communications between the air interface and the switching system. Each channel element card may support transmission of communications on a number of air interface communication channels (e.g., air interface channels, whether traffic channels or control channels) at once. In turn, a wireline trunk (e.g., a T1 line) or other link will typically couple a group of channel element cards with the switching system, transporting multiple communications at once between the cell site and the switching system.
The switching system, in turn, will then typically function to control operation of the various base transceiver stations e.g., (i) controlling handoff as mobile client stations move between base stations, and (ii) controlling allocation of air interface resources. Additionally, the switching system usually functions as a transcoder, to convert the protocol of communications being passed between the air interface and downstream network elements. For instance, in a Code Division Multiple Access (CDMA) network, the air interface may carry voice signals as Enhanced Variable Rate Codec (EVRC) encoded data, while the transport network may carry voice signals as Pulse Code Modulation (PCM) encoded data. In such a network, the switching system may include a mechanism to convert between EVRC and PCM, so as to allow voice communications to pass seamlessly between the air interface and the transport network. Other examples are possible as well.
Generally speaking, the switching system may include a number of handler modules that will function to handle cell site communications, such as to perform the protocol conversion function noted above for instance. The handler cards may then be coupled to a switching processor, which functions to route communications between the handler cards and the transport network and/or signaling network. Current state of the art is this area is reflected in the following documents, all incorporated by reference herein: Ko, U.S. Pat. No. 6,144,856; Bohlman et al., U.S. Pat. No. 6,144,646; Chheda et al., U.S. Pat. No. 6,151,512; Antonio et al., U.S. Pat. No. 6,519,456; Dolan et al., U.S. Pat. No. 6,377,572. and Choi, U.S. Pat. No. 6,278,882.
Thus, in operation, communications may pass from client stations over the air interface and through cell site channel element cards, over a T1 line to the switching system. At the switching system, the communications may then pass through handler cards to the switching processor, which may then route the communications onto a transport or signaling network. Similarly, communications may pass from a network to the switching processor and in turn through protocol handler cards and over a T1 line to a cell site. At the cell site, channel element cards may then pass the communications along to the air interface, for transmission to client stations.
As wireless networking technology advances, next-generation channel elements are rolled out in base transceiver stations from time to time by channel element vendors, such as Lucent and Motorola. The next generation channel elements are installed in cell sites side by side with other channel elements of the previous generation. For example, 70 per percent of the channel elements of a particular cell site may be second generation (“2G”) channel elements, and the remaining 30 percent may be third generation (“3G”) channel elements.
The 3G channel elements are backwards compatible with the 2G channel elements. However, there are certain types of calls that are supported by the 3G channel elements but which are not supported by the 2G channel elements. These include 3G data calls and 3G voice hand-ins.
The present inventors have observed a marked increase in the utilization of 3G channel elements. This increase is greater than expected. Simultaneously, usage of 2G channel elements is decreasing at a rate greater than expected. As a result, without management of this phenomenon, many sites are utilizing their 3G channel elements inefficiently, by basically using 3G channel elements for functions that can be performed by 2G channel elements. In many cases, cell sites are essentially running out of 3G channel element capacity when they need it, for example for increased 3G data calls or 3G voice call hand ins. (Hand-ins of 3G voice calls can be downgraded to 2G and use a 2G channel element with a success rate of greater than 95 percent, but still this could be improved as up to 5% of the calls are dropped in this scenario.) In particular, using current techniques, if all the 3G channel elements are currently fully utilized by 2G calls and a 3G data call is originated in the cell site, the call will be blocked, while 2G channel elements, which could have handled the calls, sit idly by.
The present invention addresses this problem and provides methods and apparatus for proactively managing the utilization of the channel element resources to more efficiently use the previous and next generation equipment.